Electrodeionization (EDI) is a process that removes ionized and ionizable species from liquids using electrically active media and an electrical potential to influence ion transport. In many EDI processes, ion conducting membranes and an imposed electrical current are used. Cations and anions in the feedwater are exchanged for hydrogen and hydroxyl ions in the ion exchange resin or membrane, thus producing demineralized feedwater.
Hydrogen and hydroxyl ions are needed to regenerate the exchange sites, and these are continuously regenerated in EDI processes by the electrically driven water splitting process by which H+ and OH− ions are generated. The ion conducting membranes utilized in the process are semipermeable anion and cation ion exchange membranes and are provided in stacks between electrodes with spaces between membranes configured to create fluid flow compartments. The anion membranes allow only negatively charged ions (anions) to permeate while the cation membranes allow only the positively charged ions (cations) to permeate. Ions migrating through the stack toward their opposite polarity electrodes are trapped in certain “concentrating” compartments while the influent feed is purified in so-called dilution compartments from which the salt imparting ions have vacated. The reduced ion purified product is taken from these dilution compartments to a header or the like for collection.
These EDI devices depend on the use of expensive ion exchange membranes or carbon electrodes. There is accordingly, a need in the art for a device that can perform intended deionization function that uses less expensive materials such as ion exchange beads.